I too met my wife on an internet dating site, in March 2010. we have just married. i think it is a sensible idea to take your lady friend to the uk first. will she be able to go?
i dont think there is a minimum amount of time you have to be in a relationship for. so dont worry about that. as long as you can prove to the ECO that your relationship is genuine, that is what counts. you have seen her twice and will do again in november, so that is good. just collate as much evidence as you can